A lithium nickel manganese oxide cathode material, a preparation method thereof and a secondary battery

Abstract

The application discloses a lithium nickel manganese oxide positive electrode material and a preparation method thereof and a secondary battery, and relates to the technical field of lithium ion battery positive electrode materials. The preparation method comprises the following steps: mixing a lithium source, a manganese source, a nickel source, a solvent and a complexing agent to obtain a mixed solution; drying to obtain a lithium nickel manganese oxide precursor; crushing the lithium nickel manganese oxide precursor by means of airflow milling to obtain crushed material, and performing pre-burning, sintering and annealing treatment on the crushed material; wherein the complexing agent comprises one or more combinations of sodium nitrilotriacetate, ethylenediaminetetraacetate, diethylenetriaminepentaacetate, tartaric acid, gluconic acid, organic carbonate, ethyl acetate, ethyl formate, alkene, alkyne, aromatic hydrocarbon and ethylene. The application guarantees good complexing effect and dispersion effect, and the size is uniform, the particle size is controllable, and the positive electrode material obtained by the application does not need secondary modification (doping or coating) and can obtain excellent charge-discharge performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material technology, and more specifically, to a lithium nickel manganese oxide cathode material, its preparation method, and a secondary battery thereof. Background Technology

[0002] A lithium-ion battery is a secondary battery system that uses two different lithium intercalation compounds capable of reversibly inserting and extracting lithium ions as the positive and negative electrodes, respectively. During charging, lithium ions are extracted from the crystal lattice of the positive electrode material, pass through the electrolyte, and then insert into the crystal lattice of the negative electrode material, making the negative electrode lithium-rich and the positive electrode lithium-poor. During discharging, lithium ions are extracted from the crystal lattice of the negative electrode material, pass through the electrolyte, and then insert into the crystal lattice of the positive electrode material, making the positive electrode lithium-rich and the negative electrode lithium-poor. The difference in potential between the positive and negative electrode materials relative to metallic lithium during lithium ion insertion and extraction is the battery's operating voltage.

[0003] Spinel lithium nickel manganese oxide (LiMO) is a commonly used cathode material, possessing advantages such as high theoretical capacity, high voltage plateau, excellent cycle performance, low capacity loss, low manufacturing cost, and environmental friendliness. Furthermore, its energy density reaches as high as 650 Wh / kg, making it highly promising for applications in high-energy-density lithium ions. However, despite its high theoretical capacity, the actual electrochemical performance, such as the initial discharge specific capacity, of conventional undoped or uncoated LiMO cathode materials is not high enough to meet everyday needs.

[0004] In addition, the most commonly used methods for synthesizing lithium nickel manganese oxide are solid-phase synthesis, co-precipitation, and sol-gel methods.

[0005] Solid-phase synthesis involves: accurately weighing each raw material according to a specified ratio, mechanically mixing the raw materials to obtain an initial product, grinding and dispersing to obtain an intermediate product, and calcining at high temperature to obtain the final product. While this method is simple, it suffers from problems such as uneven phase distribution, easy introduction of impurities during preparation, high required temperatures, and high energy consumption. These issues can further affect the electrochemical performance of lithium-ion batteries.

[0006] The coprecipitation method involves converting soluble salts of nickel and manganese into a coprecipitation complex, then adding lithium salt and performing solid-phase ball milling and high-temperature calcination to obtain lithium nickel manganese oxide. However, the presence of this product in the environment makes it difficult to control moisture levels, leading to excessively high internal moisture content in the battery. This, in turn, triggers a chain reaction of electrochemical reactions, promoting electrolyte decomposition and releasing large amounts of gas. In particular, after high-temperature storage, lithium nickel manganese oxide batteries accumulate a large amount of gas inside, resulting in significant battery expansion and negatively impacting battery performance.

[0007] The lithium nickel manganese oxide cathode material prepared by the sol-gel method has poor crystallinity and low purity, which affects its electrochemical performance.

[0008] The above preparation methods cannot effectively guarantee the complexation and dispersion effects, resulting in poor electrochemical performance of lithium nickel manganese oxide cathode materials.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The purpose of this invention is to provide a lithium nickel manganese oxide cathode material, its preparation method, and a secondary battery.

[0011] This invention is implemented as follows:

[0012] In a first aspect, the present invention provides a method for preparing a lithium nickel manganese oxide cathode material, comprising:

[0013] A lithium source, a manganese source, a nickel source, a solvent, and a complexing agent are mixed to obtain a mixture; the mixture is then dried to obtain a lithium nickel manganese oxide precursor.

[0014] The lithium nickel manganese oxide precursor is pulverized by an air jet mill to obtain a pulverized material, which is then subjected to pre-calcination, sintering and annealing treatments to obtain a lithium nickel manganese oxide cathode material.

[0015] The complexing agent includes one or more combinations of sodium triacetate, ethylenediaminetetraacetate, diethylenetriaminepentacarboxylate, tartaric acid, gluconic acid, organic carbonate, ethyl acetate, ethyl formate, olefins, alkynes, aromatic hydrocarbons, and ethylene.

[0016] In an optional embodiment, the amount of the complexing agent added is 10%-20% of the theoretical mass of lithium nickel manganese oxide;

[0017] Preferably, the complexing agent comprises one or more of sodium triacetate, ethylenediaminetetraacetate, and diethylenetriaminepentacarboxylate.

[0018] In an optional embodiment, the air jet mill pulverizes the material at an airflow rate of 2-4 m³ / h. 3 The process is carried out at an air pressure of 0.7-0.85 MPa, wherein the particle size of the lithium nickel manganese oxide precursor subjected to the air jet milling is <3 mm.

[0019] In an optional embodiment, the particle size of the pulverized material is D97≤2μm.

[0020] In an optional embodiment, the molar ratio of lithium, nickel, and manganese in the lithium source, the manganese source, and the nickel source is (1.00-1.06):(0.4-0.55):(1.45-1.6);

[0021] Preferably, the lithium source, the manganese source, and the nickel source are all soluble materials;

[0022] Preferably, the lithium source includes one or more combinations of lithium carbonate, lithium nitrate, or lithium hydroxide;

[0023] Preferably, the nickel source includes one or more of nickel nitrate, nickel acetate, nickel citrate, basic nickel carbonate, and nickel powder;

[0024] Preferably, the manganese source includes one or more combinations of manganese nitrate, manganese acetate, and manganese citrate.

[0025] In an optional embodiment, the pre-firing includes heat treatment at 400-600°C for 2-8 hours at a heating rate of 5-8°C / min.

[0026] In an optional embodiment, the sintering includes heat treatment at 700-900°C for 6-14 hours at a heating rate of 5-8°C / min.

[0027] Preferably, the calcination atmosphere for sintering is air, and the air flow rate is greater than 5 mL / min.

[0028] In an optional embodiment, the annealing process includes annealing at a temperature of 600–700°C for 2–12 hours.

[0029] Secondly, the present invention provides a lithium nickel manganese oxide cathode material, wherein the lithium nickel manganese oxide cathode material is prepared by the preparation method of lithium nickel manganese oxide cathode material described in any of the foregoing embodiments.

[0030] Thirdly, the present invention provides a secondary battery, the secondary battery including a positive electrode, the positive electrode including the lithium nickel manganese oxide positive electrode material described in the foregoing embodiments.

[0031] The present invention has the following beneficial effects:

[0032] This application uses a complexing agent with high complexing ability to prepare lithium nickel manganese oxide precursor, and at the same time, it uses air jet milling to pulverize the precursor. Compared with conventional grinding or mechanical pulverization, air jet milling can pulverize the precursor to the micron level, with fine particle size and uniform distribution. During the air jet milling process, there will be no local overheating phenomenon, and it can even be pulverized at low temperature. It is fast and can be completed instantly. Therefore, the bioactive components in the powder can be retained to the maximum extent, thereby producing the required high-quality products. The combination of a complexing agent with high complexing ability and air jet milling can play a synergistic role, which not only ensures good complexing effect, but also ensures good dispersion effect. The material particles are uniformly dispersed, with uniform size and controllable particle size. The lithium nickel manganese oxide cathode material prepared in this application can obtain excellent charge and discharge performance without secondary modification (doping or coating). The specific capacity of 0.1C first charge is greater than 145.50 mAh / g, the specific capacity of 1C charge is greater than 139.40 mAh / g, the specific capacity of 0.1C first discharge is greater than 137.70 mAh / g, and the specific capacity of 1C discharge is greater than 137.10 mAh / g. Compared with the specific capacity of conventional undoped or uncoated lithium nickel manganese oxide cathode materials, the charge and discharge performance is significantly improved. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a scanning electron microscope image of the lithium nickel manganese oxide cathode material provided in Example 1 of this application;

[0035] Figure 2 The X-ray diffraction pattern of the lithium nickel manganese oxide cathode material provided in Example 1 of this application;

[0036] Figure 3 This is a voltammetric scan of the lithium nickel manganese oxide cathode material provided in Example 1 of this application;

[0037] Figure 4 This is a schematic diagram of the first charge-discharge curves of the lithium nickel manganese oxide cathode material provided in Example 1 of this application at 0.1C and 1C rates. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] This invention provides a method for preparing lithium nickel manganese oxide cathode material, which includes the following steps:

[0040] S1. Preparation of lithium nickel manganese oxide precursor.

[0041] (1) Lithium source, manganese source and nickel source are added to solvent according to the molar ratio of each element in lithium nickel manganese oxide to obtain mixed solution A.

[0042] The molar ratio of lithium, nickel, and manganese in the lithium, manganese, and nickel sources is (1.00-1.06):(0.4-0.55):(1.45-1.6); all lithium, manganese, and nickel sources are soluble materials; the lithium source includes, but is not limited to, one or more combinations of lithium carbonate, lithium nitrate, or lithium hydroxide; the nickel source includes, but is not limited to, one or more combinations of nickel nitrate, nickel acetate, nickel citrate, basic nickel carbonate, and nickel powder; the manganese source includes, but is not limited to, one or more combinations of manganese nitrate, manganese acetate, and manganese citrate. The solvent includes, but is not limited to, distilled water.

[0043] (2) Add a complexing agent to the mixed solution A and mix and stir to obtain mixed solution B; dry mixed solution B to obtain lithium nickel manganese oxide precursor.

[0044] Complexing agents include, but are not limited to, one or more combinations of sodium nitrilotriacetate, ethylenediaminetetraacetate, diethylenetriaminepentacarboxylate, tartaric acid, gluconic acid, organic carbonates, ethyl acetate, ethyl formate, alkenes, alkynes, aromatic hydrocarbons, and ethylene. Preferably, the complexing agent includes one or more combinations of sodium nitrilotriacetate, ethylenediaminetetraacetate, and diethylenetriaminepentacarboxylate. The amount of complexing agent added is 10%-20% of the theoretical mass of lithium nickel manganese oxide produced. In some embodiments, the amount of complexing agent added is any one or a range between 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20% of the theoretical mass of lithium nickel manganese oxide produced.

[0045] S2, air jet milling.

[0046] The lithium nickel manganese oxide precursor was pulverized by an air jet mill to obtain a powdered material.

[0047] Air jet milling includes, but is not limited to, counter-jet air jet mills. The feed particle size (i.e., the particle size of the lithium nickel manganese oxide precursor entering the air jet mill) is <3 mm, and the air flow rate is 2-4 m³ / h. 3 The crushing speed is 0.7-0.85 MPa, the air pressure is 0.7-0.85 MPa, and the installed power is 7.5 kW. The particle size of the crushed material obtained after crushing is D97≤2 μm.

[0048] S3. Preparation of lithium nickel manganese oxide cathode material.

[0049] The pulverized material is pre-calcined, sintered, and annealed to obtain lithium nickel manganese oxide cathode material;

[0050] Specifically, the pulverized material is preheated at 400–600°C for 2–8 hours at a heating rate of 5–8°C / min, followed by sintering at 700–900°C for 6–14 hours at a heating rate of 5–8°C / min. The sintering atmosphere is air with a flow rate greater than 5 mL / min. After sintering, the material is annealed at 600–700°C for 2–12 hours.

[0051] In some embodiments, the pre-firing temperature can be, for example, any one or a range of two of 400, 450, 500, 550, 580, and 600°C, and the pre-firing time can be, for example, any one or a range of two of 2, 3, 4, 5, 6, 7, and 8 hours. The sintering temperature can be, for example, any one or a range of two of 700, 750, 800, 850, 880, and 900°C, and the sintering time can be, for example, any one or a range of two of 6, 8, 10, 11, 12, 13, and 14 hours. The annealing temperature can be, for example, any one or a range of two of 600, 650, 680, and 700°C, and the annealing time can be, for example, any one or a range of two of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 hours.

[0052] It should be noted that complexing agents can undergo complexation reactions with metal ions generated from the hydrolysis of nickel and manganese sources to form complex products. There are various types of complexing agents available, and different complexing agents contain different functional groups, resulting in varying complexing abilities. These differences in complexing ability lead to significant variations in the phase, morphology, and properties of the final product. Examples include alkanolamine complexing agents, aminocarboxylate complexing agents, and hydroxyaminocarboxylate complexing agents. Alkanolamine complexing agents, including but not limited to monoethanolamine, diethanolamine, and triethanolamine, possess some complexing ability but have relatively poor complexing capacity. They are more stable in alkaline conditions and are commonly used as complexing auxiliaries. Aminocarboxylate complexing agents and hydroxyaminocarboxylate complexing agents, on the other hand, have strong complexing abilities, high stability constants, and relatively good alkali resistance.

[0053] This application selects specific complexing agents with strong complexing power, including but not limited to one or more combinations of sodium triacetate, ethylenediaminetetraacetate, diethylenetriaminepentacarboxylate, tartaric acid, gluconic acid, organic carbonates, ethyl acetate, ethyl formate, alkenes, alkynes, aromatic hydrocarbons, and ethylene.

[0054] Meanwhile, this application uses an air jet mill to pulverize the lithium nickel manganese oxide precursor into a powder. Air jet milling pulverizes the material to the micron level, resulting in fine, uniformly distributed particles, thus resolving particle agglomeration. During the air jet milling process, localized overheating does not occur; pulverization can even be performed at low temperatures, and the process is fast and can be completed instantaneously. Therefore, it can maximize the retention of bioactive components in the powder, thereby producing the desired high-quality product and achieving a dispersing effect, controlling the uniform dispersion of material particles.

[0055] This application uses a liquid-phase method for preparation, which, compared with the solid-phase method and co-precipitation in the prior art, yields lithium nickel manganese oxide cathode materials with uniform size, controllable particle size, and excellent charge-discharge performance.

[0056] Furthermore, this application also provides a secondary battery, which includes a positive electrode comprising the aforementioned lithium nickel manganese oxide positive electrode material.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Example 1

[0059] S1. Dissolve 0.005 mol lithium carbonate, 0.015 mol manganese acetate tetrahydrate, and 0.005 mol nickel nitrate hexahydrate in a beaker containing 75 mL of aqueous solution. Add 15 mL of diethylenetriamine pentacarboxylate complexing agent and stir to obtain a black solution. Place the beaker containing the black solution in an oil bath and heat with magnetic stirring. Adjust the temperature to 120°C and continue heating for 25 minutes. Dry the mixture to obtain the black precursor.

[0060] S2. The precursor is pulverized by an air jet mill to obtain pulverized material with a diameter of D97≤1μm.

[0061] S3. Place the pulverized material in a muffle furnace and pre-calcine at 600℃ for 5 hours at a heating rate of 5℃ / min to obtain a spinel-structured nano-sized lithium nickel manganese oxide semi-finished product. After sieving the semi-finished lithium nickel manganese oxide cathode material through a 300-mesh sieve, place it in a tube furnace and sinter at 750℃ for 12 hours at a heating rate of 5℃ / min. After sintering, anneal at 700℃ for 2 hours to prepare the lithium nickel manganese oxide cathode material, such as... Figure 1 and Figure 2 As shown, from Figure 1and Figure 2 As can be seen, the scanning electron microscope image shows that the material particles are evenly distributed and there is no obvious agglomeration, and the X-ray diffraction pattern shows that the material is free of impurities.

[0062] Example 2

[0063] S1. Dissolve 0.005 mol lithium carbonate, 0.015 mol manganese acetate tetrahydrate, and 0.005 mol nickel acetate in a beaker containing 75 mL of aqueous solution. Add 15 mL of sodium triacetate complexing agent and stir to obtain a black solution. Place the beaker containing the black solution in an oil bath and heat with magnetic stirring. Adjust the temperature to 120°C and continue heating for 25 minutes. Dry the mixture to obtain the black precursor.

[0064] S2. The precursor is pulverized by air jet mill to obtain pulverized material with D97≤1μm.

[0065] S3. Place the pulverized material in a muffle furnace and pre-calcine it to 550℃ at a heating rate of 5℃ / min for 6 hours to obtain a spinel-structured nano-sized lithium nickel manganese oxide semi-finished product. After sieving the lithium nickel manganese oxide cathode material semi-finished product through a 300-mesh sieve, place it in a tube furnace and sinter it at 850℃ for 8 hours at a heating rate of 5℃ / min. After sintering, anneal it at 650℃ for 2 hours to prepare the lithium nickel manganese oxide cathode material.

[0066] Example 3

[0067] S1. Dissolve 0.0053 mol lithium carbonate, 0.016 mol manganese acetate tetrahydrate, and 0.004 mol nickel acetate in a beaker containing 75 mL of aqueous solution. Add 15 mL of ethylenediaminetetraacetic acid (EDTA) complexing agent and stir to obtain a black solution. Place the beaker containing the black solution in an oil bath and heat with magnetic stirring. Adjust the temperature to 120 °C and continue heating for 25 min. Dry the mixture to obtain the black precursor.

[0068] S2. The precursor is pulverized by air jet mill to obtain pulverized material with D97≤1μm.

[0069] S3. Place the pulverized material in a muffle furnace and pre-calcine it to 450℃ at a heating rate of 8℃ / min for 8 hours to obtain a spinel-structured nano-sized lithium nickel manganese oxide semi-finished product. After sieving the lithium nickel manganese oxide cathode material semi-finished product through a 300-mesh sieve, place it in a tube furnace and sinter it at 700℃ for 14 hours at a heating rate of 8℃ / min. After sintering, anneal it at 600℃ for 12 hours to prepare the lithium nickel manganese oxide cathode material.

[0070] Example 4

[0071] This embodiment is basically the same as Embodiment 1, except that the particle size of the pulverized material is D97≤2μm when the air jet mill is used to pulverize it.

[0072] Example 5

[0073] This embodiment is basically the same as that of Embodiment 1, except that the diethylenetriaminepentacarboxylate complexing agent in Embodiment 1 is replaced with gluconic acid.

[0074] Example 6

[0075] This embodiment is basically the same as Example 1, except that the diethylenetriaminepentacarboxylate complexing agent in Example 1 is replaced with ethyl acetate.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that the diethylenetriamine pentacarboxylate complexing agent in Example 1 is replaced with diethanolamine in this comparative example.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the diethylenetriaminepentacarboxylate complexing agent in Example 1 is replaced with citric acid in this comparative example.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 1 is that the precursor in this comparative example was not pulverized by an air jet mill.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 is that in this comparative example, the precursor pulverization by air jet milling in Example 1 is replaced by grinding of the precursor, and the particle size of the pulverized material is D97≤1μm.

[0084] Comparative Example 5

[0085] The difference between this comparative example and Example 1 is that the diethylenetriamine pentacarboxylate complexing agent in Example 1 is replaced with citric acid, and the process of pulverizing the precursor by air jet milling in Example 1 is replaced with grinding the precursor, and the particle size of the pulverized material is D97≤1μm.

[0086] Comparative Example 6

[0087] The difference between this comparative example and Example 1 is that in this comparative example, the air jet mill was used to pulverize the material until the particle size of the pulverized material was D97>2.5μm.

[0088] Experimental Example

[0089] The lithium nickel manganese oxide cathode materials obtained in the above embodiments and comparative examples are used to prepare corresponding lithium-ion batteries. The preparation method of the lithium-ion battery is as follows:

[0090] The positive electrode used the active material: conductive agent: binder ratio of 80:10:10 in the examples and comparative examples. An R2032 type battery was prepared using lithium metal sheet as the negative electrode. Testing was conducted using a Blue Electric System tester under a charge-discharge cycle of 4.95V to 3.5V. The test results are available in the reference [link to test results]. Figure 3 , Figure 4 And as shown in Table 1 below:

[0091] Table 1. Statistical table of charge and discharge performance for different examples

[0092]

[0093]

[0094] Wherein, charge / discharge efficiency = discharge specific capacity / charge specific capacity × 100%.

[0095] Comparing Example 1 and Comparative Example 1, it can be seen that selecting a complexing agent with strong complexing ability is beneficial to reducing the probability of lithium ions and nickel ions mixing in lithium nickel manganese oxide cathode materials, improving their structural stability, and thus improving the first discharge efficiency of lithium nickel manganese oxide cathode materials and enhancing electrochemical performance.

[0096] Comparing Example 1 and Comparative Example 2, it can be seen that using a complexing agent with high complexing ability to prepare lithium nickel manganese oxide precursor results in a cathode material with better electrochemical performance.

[0097] Comparing Example 1 and Comparative Example 3, it can be seen that air jet milling is beneficial for subsequent processing to form spinel-type lithium nickel manganese oxide cathode material with uniform particles and good crystal purity. Applying it to lithium-ion batteries can improve the first discharge efficiency and 1C charge-discharge effect of lithium-ion batteries.

[0098] Comparing Example 1 and Comparative Example 4, it can be seen that the dispersion effect is better, the size is more uniform, and the electrochemical performance is better after being pulverized by air jet mill.

[0099] Comparing Example 1 and Comparative Example 5, it can be seen that using a complexing agent with high complexing ability and air jet milling can achieve a synergistic effect.

[0100] Comparing Example 1 and Comparative Example 6, it can be seen that when the particle size is controlled within D97≤2μm, the material exhibits better electrochemical performance.

[0101] In summary, this application uses a complexing agent with high complexing ability to prepare lithium nickel manganese oxide precursor, and simultaneously uses air jet milling to pulverize the precursor. Compared with conventional grinding or mechanical pulverization, air jet milling can pulverize the precursor to the micron level, with fine particle size and uniform distribution. During the air jet milling process, there will be no local overheating phenomenon, and pulverization can even be carried out at low temperatures. It is fast and can be completed instantly. Therefore, the bioactive components in the powder can be retained to the maximum extent, thereby producing the required high-quality products. The combination of a complexing agent with high complexing ability and air jet milling can play a synergistic role, which not only ensures good complexing effect, but also ensures good dispersion effect. The material particles are uniformly dispersed, with uniform size and controllable particle size. The lithium nickel manganese oxide cathode material prepared in this application can obtain excellent charge and discharge performance without secondary modification (doping or coating). The specific capacity of 0.1C first charge is greater than 145.50 mAh / g, the specific capacity of 1C charge is greater than 139.40 mAh / g, the specific capacity of 0.1C first discharge is greater than 137.70 mAh / g, and the specific capacity of 1C discharge is greater than 137.10 mAh / g. Compared with the first discharge specific capacity of conventional undoped or uncoated lithium nickel manganese oxide cathode materials, the charge and discharge performance is significantly improved.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium nickel manganese oxide cathode material, characterized in that, It includes: According to the molar ratio of each element in lithium nickel manganese oxide, the lithium source, manganese source, and nickel source are added to the solvent for dissolution treatment to obtain mixed solution A; A complexing agent is added to the mixed solution A, and the mixture is stirred to obtain a mixed solution B; the amount of complexing agent added is 10%-20% of the theoretical mass of lithium nickel manganese oxide; the complexing agent includes one or more combinations of sodium nitrilotriacetate, ethylenediaminetetraacetate, and diethylenetriaminepentacarboxylate. The mixture B was dried to obtain the lithium nickel manganese oxide precursor; The lithium nickel manganese oxide precursor is pulverized by an air jet mill to obtain a pulverized material with a particle size of D97≤2μm. The pulverized material is then subjected to pre-calcination, sintering and annealing treatments to obtain a lithium nickel manganese oxide cathode material.

2. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The airflow milling process includes an airflow rate of 2-4 m³ / h. 3 The process is carried out at an air pressure of 0.7-0.85 MPa, wherein the particle size of the lithium nickel manganese oxide precursor subjected to the air jet milling is <3 mm.

3. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The molar ratio of lithium, nickel, and manganese in the lithium source, manganese source, and nickel source is (1.00-1.06):(0.4-0.55):(1.45-1.6).

4. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The lithium source, the manganese source, and the nickel source are all soluble materials.

5. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The lithium source includes one or more combinations of lithium carbonate, lithium nitrate, or lithium hydroxide.

6. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The nickel source includes one or more of nickel nitrate, nickel acetate, nickel citrate, basic nickel carbonate, and nickel powder.

7. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The manganese source includes one or more combinations of manganese nitrate, manganese acetate, and manganese citrate.

8. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The preheating process involves heating to 400-600°C at a heating rate of 5-8°C / min for 2-8 hours.

9. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The sintering process involves heating to 700-900°C at a heating rate of 5-8°C / min for 6-14 hours.

10. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The calcination atmosphere for the sintering is air, and the air flow rate is greater than 5 mL / min.

11. The method for preparing lithium nickel manganese oxide cathode material according to claim 1, characterized in that, The annealing process includes annealing at a temperature of 600~700℃ for 2~12 hours.

12. A lithium nickel manganese oxide cathode material, characterized in that, The lithium nickel manganese oxide cathode material is prepared by the method for preparing lithium nickel manganese oxide cathode material according to any one of claims 1-11.

13. A secondary battery, characterized in that, The secondary battery includes a positive electrode, which includes the lithium nickel manganese oxide positive electrode material as described in claim 12.

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